| The environmental problems of soil nitrogen and phosphorus in conventional paddy fields in China are more serious.The problems of insufficient water resources,low utilization rate of water and fertilizer resources,unstable rice yield,relatively low production efficiency and benefit restrict the production efficiency and sustainable development of China’s rice production system.In this paper,biochar,silicon residue materials and humic acid conditioner are selected under dry direct seeding,and two water-saving optimization measures are designed to deeply study the nutrient absorption and soil physical and chemical properties of dry direct seeding rice under the cultivation mode of combining soil conditioner and water optimization,so as to improve soil quality,improve water production efficiency,improve yield and quality The purpose of reducing the environmental risk of nitrogen and phosphorus is to provide a theoretical reference for the development of dry direct seeding rice cultivation in Tianjin and other production areas with prominent constraints of water and soil environmental factors.The results are as follows:（1）The results of pot experiment showed that the application of conditioner had a significant effect on the growth of dry direct seeding rice.Under the two optimized water management of dry direct seeding rice,the growth of T8 combined with full conditioner had advantages,and there was no significant difference between T8 and conventional irrigation.In terms of biomass and nutrient absorption,the application of soil conditioner can significantly promote the dry matter accumulation and nutrient absorption of dry direct seeding rice,and has a significant effect on the improvement of rice yield.The total dry matter mass and nutrient absorption are better under the condition of 30%water saving irrigation.The biomass accumulation of T8 treated with conditioner was the best,which had no significant difference from that under conventional irrigation.The single application of conditioner T3 was conducive to promote the dry matter accumulation of rice parts.In terms of nitrogen,phosphorus and potassium absorption,T2 and T8 absorption were better.In terms of soil physical and chemical properties,the combination of biochar,humic acid and three regulators can better improve the soil aggregate structure and then improve the stability of soil structure.,Under the overall water-saving irrigation of 30%,it is more conducive to improve the content of CEC,organic matter and carbon nitrogen ratio,so as to better improve the soil fertilizer retention capacity.Under the water-saving irrigation of 50%,it is more conducive to reduce the content of nitrate nitrogen,total phosphorus,available phosphorus and water-soluble phosphorus in the soil surface.The decrease of nitrate nitrogen in potted soil of each treatment was 27.49%-96.21%,and the decrease of soil water-soluble phosphorus was 10.34%-41.25%.T2 and T8 had a good effect on reducing the leaching and diffusion of soil nitrogen and phosphorus,that is,the combined application of biochar and three regulators alone had an obvious effect on increasing soil organic matter and reducing soil nitrogen and phosphorus content.In terms of soil biological properties,30%water-saving irrigation is more conducive to the activity of soil urease and soil alkaline phosphatase and the content of soil microbial biomass carbon and nitrogen.T2 and T8 treatments are more conducive to enhance the content of soil microbial biomass carbon and nitrogen,promote the activities of urease and phosphatase more obviously,and then promote the absorption of soil nitrogen and phosphorus by dry direct seeding rice plants.The application of carbon can improve the pH of soil,and the application of silicon can improve the pH of soil.（2）The field experiment results showed that the application of conditioner had a significant effect on the growth of dry direct seeding rice.In the tillering stage,30%water-saving irrigation was significantly conducive to the growth of dry direct seeding rice,while in the jointing booting stage and filling stage,50%water-saving irrigation management was more conducive to the growth,development and maturity of dry direct seeding rice.T2and T8 treatments had obvious advantages in plant height,leaf color value,leaf area and photosynthetic rate.In terms of biomass and nutrient absorption,the total dry matter mass and nutrient absorption are better under the condition of 30%water-saving irrigation.The total dry matter mass of T3 and T8 treatment is 21562.5kg/hm~2and 24235.4kg/hm~2respectively,and the rice parts T3 and T8 are 8262.8kg/hm~2and 9158.3kg/hm~2respectively,which are 95.1%and 63.5%higher than the control T1 respectively.The total nitrogen absorption of T3treatment is 132.1kg/hm~2,and the nitrogen absorption of rice is 31.3kg/hm~2,T2 The total phosphorus uptake of T8 treatment was 16.3 kg/hm~2and 17.1 kg/hm2respectively,and the total potassium uptake was 76.93 kg/hm~2and 75.56 kg/hm~2respectively.The absorption of T3 in rice part was better,and the absorption of phosphorus and potassium were 89.6%and28.34%higher than that of control T1 respectively.In terms of quality,the application of conditioner has a certain improvement on rice quality,and there is no significant difference between the two water management on rice quality.The application of silicon conditioner has a good effect on the processing appearance quality and nutritional quality of T3 and T8 rice.In terms of soil physical and chemical properties,T2 and T8 treatments can significantly promote the formation of large aggregates and better improve the soil aggregate structure.Under the condition of 50%water-saving irrigation,they can significantly reduce the soil bulk density,which is 11.11%and 6.53%higher than the control T1 under this irrigation,and increase the field water capacity by 20.28%and 26.67%.At the same time,T2 and T8treatments can significantly improve soil cation exchange capacity（CEC）,organic matter content and carbon nitrogen ratio,which is better under 30%water-saving irrigation.Under the condition of 50%water-saving irrigation,it can better reduce the contents of soil total nitrogen and total phosphorus,as well as the contents of soil nitrate nitrogen and water-soluble phosphorus.The decrease range of soil nitrate nitrogen in each treatment is7.32%-71.67%,the decrease range of available phosphorus is 0.99%-4.98%,and the decrease range of soil water-soluble phosphorus is 11.02%-65.21%.In terms of soil biological properties,under the condition of 30%water-saving irrigation,the soil urease activity of T2 and T8 treatments decreased better,with a decrease range of 0.05%-13.42%,and the soil alkaline phosphatase increased better,with an increase range of 4.08%-39.63%.The effect of T8 treatment was the best.The application of conditioner T2 and T8 alone had obvious advantages in increasing the content of soil microbial biomass carbon and nitrogen.The application of carbon can slightly improve the pH of soil,and the application of silicon can improve the pH of soil.In terms of soil nitrogen and phosphorus transport,under the condition of 30%water-saving irrigation,the transport of soil nitrogen and phosphorus is slowed down better.Compared with the basic value,the decline of nitrate nitrogen of each treatment is 1.87%-65.92%.T2 and T8 treatment have the best effect on reducing soil available phosphorus.T2and T8 treatment have the best effect on reducing soil available phosphorus in 0～30cm,30～60cm,60～90cm and 90～120cm soil layers,which can weaken the diffusion of nitrogen and phosphorus with water loss and better slow down the downward migration of nitrogen and phosphorus,Reduce soil environmental risks.Comprehensive pot and field experiments,combined with crop growth,yield,nitrogen,phosphorus and potassium nutrient absorption,improvement of soil physical and chemical properties and quality improvement,the combined application of biochar（T2）and biochar+silicon conditioner+humic acid（T8）has a better comprehensive effect,and the effect is better under 30%water-saving irrigation. |
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